Using inherited containers

[jimbo1999]

Hi,

I've created a class SetOfPersons which holds an array of Person object pointers (Person ** elements

I've also created a subclass - SetOfAdults which inherits from SetOfPersons. Also I have an Adult class that inherits from Person.

In my main method I have:
Adult *a1 = new Adult("Name", 98); //constructor is (name, age).
SetOfAdults adults;
adults.add(*a1);

Later I try:
Adult & a2 = adults.getNextElement();

The compiler gives me:
cannot convert from 'class Person' to 'class Voter &'

Where am I going wrong? Should the SetOfPersons be modified?

Thanks,
jimbo.

 

[timmay3141]

First, main() is a global function, a method must be a member of a class.

Second, I'll assume that getNextElement() returns a Person, but you must realize that a Person is not necessarily an Adult. If you want to use polymorphism, you should have it return a pointer to a Person instead, and then just type cast it to an Adult*.

Third, this isn't Java - functions should use Pascal casing in C++.

 

[cpjust]

Is class Voter derived from class Adult?
How are your classes inherited (i.e. in the header code)?

 

[jimbo1999]

Sorry, should read Adult, not voter.

I have:
class Person {...}
class Adult : public Person{...}

then
class SetOfPersons {...}
and class SetOfAdults : public SetOfPersons {...}

Is there a way to convert a Person reference to an adult reference when it is returned from SetOfAdults? Because all I get returned at the moment is a Person reference.

 

[teriviret]

I don't think you can convert a reference that way. If it was a pointer instead of a reference, you could use either dynamic_cast<> or static_cast<> to convert from Person* to Adult*. Use dynamic_cast<> if RTTI is enabled and you're not sure whether or not the Person is really an Adult. If you're sure it is an adult, use static_cast<> instead.